Altogether, the world's subway systems provide a captive audience of 80 million viewers. And many of them have money to spend.
Tunnel advertising has greater recall than any other advertising medium, including out-of-home.
The memory recall of tunnel advertising is almost double that of conventional station advertising. For this reason this medium is expected to be the medium of century for outdoor advertising in Metro Systems.

More in tune with competition – competing street furniture is going this way – e.g. plasma displays, large LED display systems in high profile locations.
Keeps high profile – Passenger counts are very high and cost per person is low when compared to other media.
Panels may be any size - Uses proven technology for image positioning and manipulation
Fully covered by patent application.

Larger displays – LCD panels provide much larger displays than that is possible with most poster based systems which are limited by train speed.
HDTV – Image quality will use full capability of available panels, which are known to be HDTV quality.
Both directions – The video presentation can be made in either direction, allowing the system to be better employed when a section of tunnel operates in both directions. In this case poster based systems will only show for trains in one direction.

Easier selling process – Selling smaller 'slots' is easier than selling a block booking for a month as required with the poster based systems
No printing costs or delays – The route from video to uploaded advertisement is simple and may be transacted completely online.
Better sales targeting – Advertisements may be scheduled to suit the time of day (e.g. coffee in the morning, shopping in the afternoon, alcoholic beverages and places to go in the evening)